Swallowing and esophageal motility !

Mechanism
Exam priority: medium

Swallowing starts voluntarily and continues as an automatic reflex that seals the airway and pushes the bolus into the stomach in a few seconds.

Updated 2026-11-01

Also called: Esophageal peristalsis, Lower esophageal sphincter

See it in 3D: Tongue · Soft palate · Pharynx · Pharyngeal constrictors · Esophagus · Stomach · Vagus nerve · Medulla oblongata

Key points

Pharyngeal phase (≈1 s): the soft palate seals the nasopharynx, the larynx rises, the epiglottis tilts, the vocal folds close and breathing is inhibited.
Swallowing centre in the medulla and lower pons; afferents via V, IX and X, efferents via V, VII, IX, X and XII.
Primary peristalsis continues a swallow; secondary peristalsis is triggered by distension from a bolus left behind.
The upper third of the esophagus is striated muscle; the lower two thirds are smooth muscle run by the myenteric plexus.
The lower esophageal sphincter keeps a tone of ≈10–30 mmHg and relaxes (VIP and nitric oxide, receptive relaxation) as soon as a swallow begins.
Achalasia: loss of inhibitory neurons → a sphincter that will not relax and aperistalsis; in Colombia, Chagas disease causes a secondary form.

What it is

Swallowing has a voluntary oral phase, a reflex pharyngeal phase coordinated by the brainstem swallowing centre, and an esophageal phase in which a peristaltic wave carries the bolus to the stomach. The upper and lower esophageal sphincters stay closed between swallows and relax at exactly the right moment. When relaxation fails, achalasia results; when closure fails, reflux.

How it works, step by step

The tongue pushes the bolus against the hard palate toward the oropharynx (oral phase, voluntary).
Pharyngeal receptors activate the swallowing centre, which runs a fixed motor programme.
The soft palate seals the nasopharynx and the larynx rises under the tongue base; the epiglottis covers the laryngeal inlet.
The upper esophageal sphincter (cricopharyngeus) relaxes and the pharyngeal constrictors push the bolus into the esophagus.
A peristaltic wave travels the esophagus in ≈8–10 s; gravity helps but is not needed.
Vagal inhibitory neurons relax the lower esophageal sphincter and the proximal stomach before the bolus arrives.
The sphincter closes again; the crural diaphragm and the angle of His help prevent reflux.

Approximate values (manometry)

Parameter	Value	Note
Resting lower esophageal sphincter pressure	≈10–30 mmHg	varies with technique
Duration of the pharyngeal phase	≈1 s
Esophageal transit of a bolus	≈8–10 s	upright, faster for liquids

Approximate values for a healthy adult at rest; each laboratory sets its own ranges.

Clinical notes

Oropharyngeal dysphagia (after a stroke): coughing or choking on swallowing and a risk of aspiration pneumonia.
Achalasia: dysphagia to solids and liquids from the start, regurgitation and a dilated esophagus with a distal 'bird's beak' narrowing.
GERD: transient sphincter relaxations, hiatal hernia or low tone; typical symptom: heartburn after meals or on lying down.
Progressive dysphagia to solids only with weight loss: think of mechanical obstruction (esophageal cancer).

Test yourself

Think of the answer, then tap the question to see it.

What mechanism explains why the lower esophageal sphincter fails to relax in achalasia?

The inhibitory myenteric neurons that release VIP and nitric oxide are lost; without them there is no receptive relaxation and excitatory cholinergic tone goes unopposed.

What is the difference between primary and secondary esophageal peristalsis?

Primary follows the pharyngeal phase of a swallow. Secondary is triggered by local esophageal distension, such as a retained bolus or reflux, without a new swallow.

Why is achalasia dysphagia for both solids and liquids from the start, unlike esophageal cancer?

In achalasia the problem is motor: peristalsis and sphincter relaxation fail for everything swallowed. A tumour narrows the lumen progressively, so solids get stuck first.

Which structures protect the airway during the pharyngeal phase of swallowing?

The soft palate seals the nasopharynx, the larynx rises, the epiglottis covers the laryngeal inlet, the vocal folds close and the swallowing centre inhibits breathing.

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See it in 3D

The structures of Durgical's 3D anatomy where it happens.

In Pharmacology

Proton pump inhibitors (PPIs)

← All of physiology

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: 23.3 The Mouth, Pharynx, and Esophagus (OpenStax (Rice University), 2022); Anatomy, Head and Neck, Swallowing (StatPearls (NCBI Bookshelf), 2024); Achalasia (StatPearls (NCBI Bookshelf), 2024); Gastroesophageal Reflux Disease (GERD) (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 64). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

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Representative model, for educational purposes only.